Abstract
Durability and resilience of marine infrastructure in India are significantly impacted by the chloride-rich coastal environment, leading to reinforcement corrosion and reduced structural performance. Glass Fiber Reinforced Polymer (GFRP) bars have emerged as a promising alternative to steel reinforcement to address corrosion issues. Simultaneously, the use of seawater in concrete production has gained attention due to growing freshwater scarcity. However, there is a need to develop the Indian standards for use of seawater concrete systems integrated with GFRP reinforcement which is lacking to advance this sustainable technology. This study investigates the fresh (Initial and final setting time, Slump), mechanical (Compressive strength, split tensile strength and Elastic modulus) and durability (Water absorption, capillary absorption and homogeneity) properties of seawater concrete in comparison to conventional concrete. Two curing regimes (seawater and limewater) were considered to assess performance up to 90 days. Additionally, 0.25 % polypropylene (PP) fibers were incorporated to evaluate their influence on mechanical properties and shrinkage. Results indicated that seawater concrete exhibited better early-age strength (7 days) by 4–5 % but declined by 7–8 % at later ages (after 28 days) when cured in seawater compared to conventional concrete indicating a comparable performance. However, limewater-cured seawater concrete showed higher degradation in mechanical strength by 15–17 % at later ages (after 28 days) due to leaching. The inclusion of PP fibers led to a 10 % reduction in shrinkage. Microstructural analysis confirmed that seawater-cured mixtures are found with higher content of Ettringite and Friedel’s salt which tends to fill the pores and results in higher mechanical strength. These findings highlight the viability of using seawater for coastal infrastructure, and provide a strong foundation to incorporate relevant provisions into ACI 243 and IS 456–2000 to advance such sustainable technology.
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•Lime water curing showed strength loss of 15–17 % for seawater mixtures.•Polypropylene fibers reduced shrinkage by around 10 %.•Increased Friedel’s salt and Ettringite formation improved mechanical strength.•Seawater concrete showed comparable performance statistically.•Recommendations/suggestions to update Indian standard specifications.